ember-router-scroll

ember-router-scroll
==============================================================================


> Scroll to page top on transition, like a non-SPA website. An alternative scroll behavior for Ember applications.

Why Use it?

Ember expects an application to be rendered with nested views. The default behavior is for the scroll position to be
preserved on every transition. However, not all Ember applications use nested views. For these applications, a user
would expect to see the top of the page on most transitions.

In addition to scrolling to the top of the page on most transitions, a user would expect the scroll position to be
preserved when using the back or forward browser buttons.

ember-router-scroll makes your single page application feel more like a regular website.

Compatibility
------------------------------------------------------------------------------

* Ember.js v3.12 or above
* Ember CLI v3.12 or above
* Node.js v12 or above

Installation
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``sh
ember install ember-router-scroll
`


Usage > 4.x
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Users do not need to import and extend from ember-router-scroll anymore. In order to upgrade, you should remove this import.

This is what your router.js should look like.

`js
import EmberRouter from '@ember/routing/router';

export default class Router extends EmberRouter {
...
}
`

Usage < 4.x
------------------------------------------------------------------------------

1. Import ember-router-scroll

Add RouterScroll as an extension to your Router object. This class extends EmberRouter.

`javascript
// app/router.js

import EmberRouterScroll from 'ember-router-scroll';

class Router extends EmberRouterScroll {
...
}
`

In version prior to v2.0, you can import the mixin and use it like so. This is necessary if your application does not support JavaScript classes yet.

`javascript
// app/router.js

import RouterScroll from 'ember-router-scroll';

const Router = EmberRouter.extend(RouterScroll, {
...
});
`

Remaining optional steps for all versions 2.x - 4.x
------------------------------------------------------------------------------

2. Enable historySupportMiddleware in your app

Edit config/environment.js and add historySupportMiddleware: true, to get live-reload working in nested routes.
(See Issue #21)

`javascript
historySupportMiddleware: true,
`

This location type inherits from Ember's HistoryLocation.
`

$3

#### Target Elements

If you need to scroll to the top of an area that generates a vertical scroll bar, you can specify the id of an element
of the scrollable area. Default is window for using the scroll position of the whole viewport. You can pass an options
object in your application's config/environment.js file.

`javascript
ENV['routerScroll'] = {
scrollElement: '#mainScrollElement'
};
`

If you want to scroll to a target element on the page, you can specify the id or class of the element on the page. This
is particularly useful if instead of scrolling to the top of the window, you want to scroll to the top of the main
content area (that does not generate a vertical scrollbar).

`javascript
ENV['routerScroll'] = {
targetElement: '#main-target-element' // or .main-target-element
};
`

#### Scroll Timing

You may want the default "out of the box" behaviour. We schedule scroll immediately after Ember's render. This occurs on the tightest schedule between route transition start and end.

However, you have other options. If you need an extra tick after render, set scrollWhenAfterRender: true. You also may need to delay scroll functionality until the route is idle (approximately after the first paint completes) using scrollWhenIdle: true in your config. scrollWhenIdle && scrollWhenAfterRender defaults to false.

This config property uses ember-app-scheduler, so be sure to follow the instructions in the README. We include the setupRouter and reset. This all happens after routeDidChange.

`javascript
ENV['routerScroll'] = {
scrollWhenIdle: true // ember-app-scheduler
};
`

Or

`js
ENV['routerScroll'] = {
scrollWhenAfterRender: true // scheduleOnce('afterRender', ...)
};
`
I would suggest trying all of them out and seeing which works best for your app!

A working example

See demo made by Jon Chua.

A visual demo

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!before-scroll

Notice that the in the full purple page, the user is sent to the middle of the page.

$3

!after-scroll

Notice that the in the full purple page, the user is sent to the top of the page.

Issues with nested routes

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!before-preserve

Notice the unwanted scroll to top in this case.

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!after-preserve

Adding a query parameter or controller property fixes this issue.

$3

In certain cases, you might want to have certain routes preserve scroll position when coming from a specific location.
For example, inside your application, there is a way to get to a route where the user expects scroll position to be
preserved (such as a tab section).

1. Add query param in controller

Add preserveScrollPosition as a queryParam in the controller for the route that needs to preserve the scroll position.

Example:

`javascript
import Controller from '@ember/controller';

export default class MyController extends Controller {
queryParams = [
'preserveScrollPosition',
];
}
`

2. Pass in query param

Next, in the place where a transition is triggered, pass in preserveScrollPosition=true. For example

`handlebars

`

$3

In other cases, you may have certain routes that always preserve scroll position, or routes where the controller can
decide when to preserve scroll position. For instance, you may have some nested routes that have true nested UI where
preserving scroll position is expected. Or you want a particular route to start off with the default scroll-to-top
behavior but then preserve scroll position when query params change in response to user interaction. Using a controller
property also allows the use of preserveScrollPosition without adding this to the query params.

1. Add query param to controller

Add preserveScrollPosition as a controller property for the route that needs to preserve the scroll position.
In this example we have preserveScrollPosition initially set to false so that we get our normal scroll-to-top behavior
when the route loads. Later on, when an action triggers a change to the filter query param, we also set
preserveScrollPosition to true so that this user interaction does not trigger the scroll-to-top behavior.

Example:

`javascript
import Controller from '@ember/controller';
import { action } from '@ember/object';

export default class MyController extends Controller {
queryParams = ['filter'];

preserveScrollPosition = false;

@action
changeFilter(filter) {
this.set('preserveScrollPosition', true);
this.set('filter', filter);
}
}
`

2. Reset preserveScrollPosition if necessary

If your controller is changing the preserveScrollPosition property, you'll probably need to reset
preserveScrollPosition back to the default behavior whenever the controller is reset. This is not necessary on routes
where preserveScrollPosition is always set to true.

`javascript
import Router from '@ember/routing/route';

export default class MyRoute extends Route {
resetController(controller) {
controller.set('preserveScrollPosition', false);
}
}
`

$3

You may need to programatically control preserveScrollPosition directly from a component. This can be achieved by toggling the preserveScrollPosition property on the routerScroll service.

One common use case for this is when using query-param-based pagination on a page where preserveScrollPosition is expected to be false.

For example, if a route should always scroll to top when loaded, preserveScrollPosition would be false. However, a user may then scroll down the page and paginate through some results (where each page is a query param). But because preserveScrollPosition is false, the page will scroll back to top on each of these paginations.

This can be fixed by temporarily setting preserveScrollPosition to true on the service in the pagination transition action and then disabling preserveScrollPosition after the transition occurs.

Note: if preserveScrollPosition is set to true on the service, it will override any values set on the current route's controller - whether query param or controller property.


1. Manage preserveScrollPosition via service

When you need to modify preserveScrollPosition on the service for a specific transition, you should always reset the value after the transition occurs, otherwise all future transitions will use the same preserveScrollPosition value.

Example:

`javascript
import Component from '@glimmer/component';
import { inject as service } from '@ember/service';
import { action } from '@ember/object';

export default class MyComponent extends Component {
@service routerScroll;
@service router;

@action
async goToPaginationPage(pageNumber) {
this.set('routerScroll.preserveScrollPosition', true);
await this.router.transitionTo(
this.router.currentRouteName,
{
queryParams: { page: pageNumber }
}
);

// Reset preserveScrollPosition after transition so future transitions behave as expected
this.set('routerScroll.preserveScrollPosition', false);
}
}
`

Running Tests

* npm test (Runs ember try:testall to test your addon against multiple Ember versions)
* ember test
* ember test --serve

License
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This project is licensed under the MIT License.